1. Field of the Invention
The present invention relates to a substrate production apparatus for producing a substrate for a display device, and more particularly, to a substrate production apparatus for producing a substrate for a display device using an MMG (Multi Model on a Glass) method.
2. Description of the Related Art
As information technology continues to develop, a demand for display devices in various forms is increasing. Accordingly, there have recently been researches on several types of display devices, such as a liquid crystal display LCD, a plasma display panel PDP, an electro-luminescent display ELD, a vacuum fluorescent display VFD, and so on. Some of these display devices have already been commercially developed and used as display devices in various existing electronic systems.
Among these display devices, the LCD produces an excellent picture quality, and has advantages of being light and thin and of consuming low power. Thus, the LCD has most widely been used as a substitute for a cathode ray tube CRT for use in portable information equipment, such as notebook computers. In addition, the LCD has been developed in various ways for use in desktop computer monitors and in television sets which receive broadcast signals to display picture images. However, the continued development of the LCD as a general screen display device in various systems depends on whether the LCD can attain a high quality picture of high precision, high brightness, large display area, and so on while maintaining its advantages of being light and thin, and of consuming low power.
An LCD generally includes a liquid crystal display panel to display a picture and a driver circuit to apply drive signals to the liquid crystal display panel. The liquid crystal display panel includes first and second glass substrates and a liquid crystal layer injected between the first and second glass substrates. The first substrate is a thin film transistor TFT substrate, and the second substrate is a color filter substrate.
The TFT substrate array includes a plurality of gate lines extending horizontally at fixed intervals and a plurality of data lines at fixed intervals extending in a vertical direction perpendicular to the gate lines. A plurality of pixel electrodes is formed in a matrix shape at pixel areas which are defined by intersections of the gate lines and the data lines. TFTs are provided at the intersections of gate lines and data lines and are connected to corresponding pixel electrodes. The signals to gate lines switch the corresponding TFTs on or off to transmit signals on the data lines to corresponding pixel electrodes.
The color filter substrate includes a black matrix layer to intercept a light outside the pixel areas; R, G, and B color filter layers to express colors; and a common electrode to help attain a picture. Alternatively, in an in-plane switching mode LCD, the common electrode is formed along with the pixel electrode on the first glass substrate. The first and second glass substrates are bonded together using a seal pattern, which has a liquid crystal injection hole and a spacer to maintain a fixed gap between the first and second substrates. Then, a liquid crystal material is injected into the gap between the first and second substrates through the injection hole.
A plurality of the first and second glass substrates can be made out of a large glass substrate (hereinafter, referred to as “a mother substrate”) by performing a scribing process inclusive of cutting, a grinding process, and a cleaning process on the mother substrate.
To increase the production efficiency of the LCD panel glass substrate, a multi-model-on-a-glass (hereinafter, referred to as “MMG”) method has recently been developed. The MMG method is a method with which glass substrates of various sizes are produced from one mother substrate to increase the production efficiency. Before the MMG method was developed, it was a general practice that only LCD panel glass substrates of the same dimensions were produced from one mother substrate. The remaining space on the mother substrate was wasted without being used because of a low yield of the LCD panel glass substrate and due to difficulties in the manufacturing process when attempts were made to utilize the remaining space. For example, in a fifth generation line using a 1100×1250 mm mother substrate, twelve pieces of 17″ glass substrates or fifteen pieces of 15″ glass substrates can be produced out of one mother substrate. However, there are spaces at the outer areas of the mother substrate that are not used. Thus, in practice, a glass area use efficiency, which is calculated by dividing the sum of the areas of the LCD panel glass substrates by the total area of the mother substrate, is in a range between about 70% and about 80%.
In contrast, if an MMG method is employed, large size panel glass substrates and smaller size panel glass substrates can effectively arranged on a single mother substrate to increase the glass area use efficiency of the mother substrate to 90% or higher. Accordingly, if the MMG method is employed in the above example of the fifth generation line, while the output of twelve pieces of 17″ glass substrates from a single mother substrate is maintained, smaller size panel glass substrates, e.g., seven pieces of 7″ panel glass substrates can be additionally produced from the same mother substrate. Typically, with the use of the MMG method, glass substrates ranging in size from 5″ to about 8″ can be additionally produced from a mother substrate while the output of the existing medium to large size panel glass substrates from the same mother substrate is maintained.
As described above, the scribing process inclusive of cutting, the grinding process and the cleaning process are sequentially performed in order to produce a plurality of panel glass substrates from a mother substrate. These production processes take place in a substrate production apparatus. Hereinafter, with reference to FIGS. 1 and 2, a substrate production apparatus employing the MMG method according to the related art is discussed.
FIGS. 1 and 2 are diagrams illustrating the substrate production apparatus employing the MMG method according to the related art. FIG. 1 is a diagram showing a main model production, and FIG. 2 is a diagram depicting a sub model production. Here, the main model MM is a glass substrate of about 17″ or 15″, and the sub model SM is a glass substrate of about 8″ or 5″.
As shown in FIGS. 1 and 2, the substrate production apparatus according to the related art includes a loading part 20a, 20b to load a mother substrate 10; a scriber 30a, 30b to scribe the loaded mother substrate 10; a grinder 40a, 40b to grind a cut part after cutting the scribed mother substrate 10 in a scribed shape; a cleaning unit 50a, 50b to clean the ground glass substrate; and an unloading part 60a, 60b to unload the cleaned glass substrate. The related art substrate production apparatus further includes a transfer device (not shown) to move the glass substrate between the parts within the substrate production apparatus.
As described above, the mother substrate 10 is cut in the scribed form by the scriber 30a, 30b, and then the cut part is appropriately ground by the grinder 40a, 40b. However, the grinder 40a, 40b is set to the particular dimensions of a selected model. Thus, if another model with different dimensions is input to the grinder 40a, 40b, an error may occur in the grinding operation.
In the related art apparatus, as shown in FIGS. 1 and 2, if another model with dimensions different from the pre-selected model is received, a buffer unit 70a, 70b is installed at the input part of the grinder 40a, 40b to store the non-selected model temporarily. For example, in the event that the grinder 40a and the cleaning unit 50a conducting the production process of the main model MM are installed in the substrate production apparatus, as shown in FIG. 1, the sub models SM cannot be properly processed by the grinder 40a. Thus, the sub models SM are not transferred to the grinder 40a, but are instead moved to the buffer unit 70a in a dotted line direction, shown in FIG. 1, to be temporarily stored. In contrast, the main models MM are transferred to the cleaning unit 50a through the grinder 40a along a solid line direction, shown in FIG. 1, to be processed. The operation is performed by a hand robot (not shown).
On the other hand, in the event that the grinder 40b corresponding to the sub model SM is installed as shown in FIG. 2, i.e., the devices inclusive of the grinder 40a which are adjusted to the dimensions of the main model MM in FIG. 1 are all replaced with devices that can process the sub model SM, the sub models SM temporarily stored at the buffer unit 70b are transferred to the cleaning unit 50b through the grinder 40b along the dotted line.
As described above, due to a technical limit in the substrate production apparatus employing the MMG method according to the related art, the grinding device and the cleaning device corresponding to a selected model are pre-installed. Thus, models with dimensions different from the pre-selected model cannot be processed at the same time. In order to process different models with the related art substrate production apparatus, the grinding device and the cleaning device must be replaced with the devices which are appropriate for different dimension of the models to carry out the production process. That is, even the two groups of glasses having different dimensions are prepared in the same scribing process at the same time, the following processes for grinding and cleaning the prepared glasses should be performed in a different processing line. Therefore, after preparing two groups of glasses, one group should be preserved in a buffer unit while the other group of glasses is proceeding with the grinding and cleaning devices. After replacing the grinding and cleaning devices with another specification satisfying the preserved group of glasses, the preserved group is proceeding with the grinding and cleaning process. Accordingly, the production operation becomes more complicated, and the productivity decreases.